Research on different environmental factors that may affect seed germination and plant growth is a step towards understanding the mechanism of plant behavior and it enables us to have more control on our agricultural investment and productivity. Gravity is one of the factors that needs to be studied and understood. If you've ever planted seeds in the ground, perhaps you have wondered just how do they know which way to grow. How do the roots know to grow down and how do the stems and leaves know to grow up? Is it gravity, moisture or light that makes the root grow downward and stem grow upward?